1. Introduction

It is anticipated that the guidelines will be added to or updated while
the protocol specification remains unchanged. To facilitate this, the
guidelines are separated out into a set of documents for which this
document is a table of contents.

2. General Guidelines

These guidelines describe best practices and discuss implementation issues
for repository implementers. Topics include: minimal repository implementation;
datestamps and granularity; best practices for the use of
resumptionTokens; collection and set descriptions; flow control
and load balancing; response compression; and error handling.

These guidelines discuss issues specific to systems that act as both
harvesters and repositories. Topics include:
identifiers; provenance; and datestamps.

3. Guidelines for Optional Containers

There are a number of places in OAI-PMH responses where XML complying with
any external schema may be supplied. These containers are provided for
extensibility and for community specific enhancements. The following
sections list the optional containers and link to existing schemas.

3.1 Repository-level <description> container

The response to an Identify request may contain
description containers that can be used to express properties of the
repository that are not covered by the standard response to the
Identify verb. The following guidelines are provided:

oai-identifier:
a specification describing a specific, recommended implementation of
unique identifiers
which repositories may adhere to;rightsManifest:
part of the guidelines for conveying rights expressions than can be used
to include a manifest of rights statements that apply to metadata from
items in the repository;eprints:
a schema that can be used to provide collection-level metadata for
eprint repositories;friends:
a recommended schema allowing a repository to list confederate repositories
as a means to support automatic discovery of repositories by harvesters;branding:
a schema for repositories to provide branding information;gateway:
a schema than can be used to describe a gateway which is acting as
an OAI-PMH repository.

3.2 Set-level <setDescription> container

The response to a ListSets request may contain
setDescription containers, which provide an extensible
mechanism for communities to describe their sets.
Dublin Core metadata may be used for this purpose. A schema for
unqualified Dublin Core
is provided in the protocol document. The
Guidelines for Repository
Implementers makes further recommendations about schema that can be used
for this purpose. Other schema that may be used at the set level include:

rightsManifest:
part of the guidelines for conveying rights expressions than can be used
to include a manifest of rights statements that apply to metadata from
items in the set;branding:
a schema for repositories to provide branding information.

3.3 Record-level <metadata> container

Dublin Core metadata with metadataPrefixoai_dc is mandatory and is described in the
protocol document.
In addition, schema descriptions for the following metadata
formats are provided:

rfc1807:
a schema for rfc1807 format metadata;
marc21:
a recommended schema for MARC21 metadata, provided by the Library of Congress;
oai_marc:
a schema for MARC format metadata.

3.4 Record-level <about> container

A record may contain <about> containers that
provide information about the <metadata>
part of the record. It is expected that community specific standards
may arise in addition to the following specifications:

provenance:
a schema that is recommended for the description of the provenance
of metadata that is re-exposed by a repository, i.e. metadata
that has previously been harvested before being exposed by the repository;rights:
a specification for conveying rights expressions that pertain to
the <metadata> part of the record.

5. Community Guidelines

Individual OAI user communities are encouraged to endorse particular
formats and schemas, perhaps including some of those listed above, and
to define additional standards that meet their own needs. The following
community specific guidelines are available:

Open Language Archives Community
- a partnership of institutions and individuals who are creating a worldwide virtual library
of language resources. Includes a specific metadata format and instructions for data providers.